21ST CENT.ASTRONOMY(LL)W/CODE WKBK PKG.
6th Edition
ISBN: 9780393874921
Author: PALEN
Publisher: Norton, W. W. & Company, Inc.
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Chapter 21, Problem 25QP
To determine
Explain the reason why the relationship between recession velocity and redshift fails for distant galaxies.
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An observational survey of distant galaxies is undertaken that involves measuring their
distances using cepheid variables and red-shifts using spectroscopy. Explain how cepheid
variables can be used to measure the distances to galaxies.
A spectral line is observed whose wavelength in the laboratory is de
length of this spectral line observed in each galaxy, Xo, is listed in the table, along with
the distance, d, to the galaxy. Determine the red-shift and the recession velocity of each
galaxy and tabulate your results by making a copy of the table and filling in the blank spaces.
Sketch a Hubble diagram using your results and determine the value of the Hubble constant
Ho in units of km s-1 Mpc.
650 nm. The wave-
Galaxy 1
652.69
Galaxy 2 Galaxy 3 Galaxy 4 Galaxy 5
653.01
do (nm)
d (Mpc)
658.54
662.18
681.63
17
19
54
77
200
v (km s-1)
why are the shells visible around some elliptical galaxies significant?
Pretend that galaxies are spaced evenly, 8.0 Mpc apart, and the average mass of a galaxy is 1.0 ✕ 1011 M. What is the average density (in kg/m3) of matter in the universe?
Which model universe does this density value support?
Chapter 21 Solutions
21ST CENT.ASTRONOMY(LL)W/CODE WKBK PKG.
Ch. 21.1 - Prob. 21.1CYUCh. 21.2 - Prob. 21.2CYUCh. 21.3 - Prob. 21.3ACYUCh. 21.3 - Prob. 21.3BCYUCh. 21.4 - Prob. 21.4CYUCh. 21 - Prob. 1QPCh. 21 - Prob. 2QPCh. 21 - Prob. 3QPCh. 21 - Prob. 4QPCh. 21 - Prob. 5QP
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- Pretend that galaxies are spaced evenly, 7.0 Mpc apart, and the average mass of a galaxy is 1.0 ✕ 1011 M. What is the average density (in kg/m3) of matter in the universe? (Note: The volume of a sphere is 4/3pieR^3 and the mass of the sun is 2.0 ✕ 1030 kg.) ______ kg/m^3 Which model universe does this density value support? A: open B: flat C: closedarrow_forwardThe surface brightness profiles of elliptical galaxies follow the Sersic formula with n = 4. How much fainter is the elliptical galaxy at a radius of r compared r0 (the radius at which the brightness falls off by a factor of e), or in other words, what is the ratio of I(r)/I0. Values: r = 14 r0arrow_forwardSuppose you have obtained spectra of several galaxies and have measuerd the observed wavelength of the H-Alpha line (rest wavelength = 656.3 nm) to be Galaxy 1: 658.1 nm. Galaxy 2: 667.1 nm. Galaxy 3: 677.6 nm. Calculate the redshift, z, for each galaxy.arrow_forward
- An 800 nm spectral line when observed from a galaxy is shifted to 920 nm. Calculate the redshift.arrow_forwardThe Hubble Law, equation (D), can be used to determine the age of the universe. Using your average valueof H, calculate the recessional velocity of a galaxy of a galaxy which is 800 Mpc away.Velocity of a galaxy 800 Mpc away: _______________________________km/secarrow_forwardDistribution of Dark matter The most mass of our Milky Way is contained in an inner region close to the core with radius R0.Because the mass outside this inner region is almost constant, the density distribution can bewritten as following (assume a flat Milky Way with height z0):ρ(r) = (ρ0, r ≤ R00, r > R0(a) Derive an expression for the mass M(r) enclosed within the radius r.(b) Derive the expected rotational velocity of the Milky Way v(r) at a radius r.arrow_forward
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